Recently, the performance of portable devices has been remarkably increasing. It is desired that power sources of such portable devices are small and have a high capacity. While, the manufacturing of high-capacity batteries becomes difficult as the sizes of the batteries become small.
Patent Literature 1 discloses a battery that includes a small cylindrical metal can, a winding-type electrode group accommodated in the metal can, and a sealing member for sealing an opening in the metal can. In order to suppress an internal short circuit, a ring-shaped insulating member is disposed between an end surface of the electrode group and the sealing member. For the same purpose, in Patent Literature 2, a plate-shaped insulating ring is covered on the end surface of the electrode group.